This is more about structuring the terms and conditions (T&C) of your affiliate program and enforcing affiliate compliance than structuring affiliate commission.
Draft very clear affiliate program T&Cs with an emphasis on highlighting marketing practices your affiliates are prohibited. Make it prominent that prohibited practices will result in a reversal of commission. Allow a sufficient period of time between a sale and commission payment to allow your affiliate manager to audit for compliance and reverse commissions if necessary. Incentivize your affiliate manager to enforce these rules. If their only metric is revenue generated, they will focus on generating sales, instead reward your affiliate manager for compliance enforcement in addition to revenue.
Be selective as to whom you accept into your affiliate program. Collect and verify affiliate contact information. Interview each prospective affiliate and highlight what behaviour is not acceptable and would result in commission reversal.
Include examples of acceptable / prohibited practices in your affiliate training materials should.
If you have any follow up questions I'd be happy to hop on a call with you.
You can have websites and blogs in the supplement or weight loss niches and have no issues, as long as you don't create false testimonials, made up reviews, and things like that. When you create fake blogs and false testimonials, etc. that's when you can get into issues. I recommend giving away a bunch of your products to family, friends, and other people you might know that need the product, then ask them to review their experience on your website in the form of product reviews.